We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.
The addition of O 2 to gas mixtures in time projection chambers containing CS 2 has recently been shown to produce multiple negative ions that travel at slightly different velocities. This allows a measurement of the absolute position of ionising events in the z (drift) direction. In this work, we apply the z-fiducialisation technique to a directional dark matter search. We present results from a 46.3 live-day source-free exposure of the DRIFT-IId detector run in this new mode. With full-volume fiducialisation, we have achieved the first background-free operation of a directional detector. The resulting exclusion curve for spindependent WIMP-proton interactions reaches 1.1 pb at 100 GeV/c 2 , a factor of 2 better than our previous work. We describe the automated analysis used here, and argue that detector upgrades, implemented after the acquisition of these data, will bring an additional factor of 3 improvement in the near future.arXiv:1410.7821v3 [hep-ex] 23 Jul 2015 DRIFT-IId detector and science runsThe DRIFT experiment is sited at a depth of 1.1 km in the STFC Boulby Underground Science Facility [29], which provides 2805 m.w.e. shielding against cosmic rays. The TPC is housed inside a stainless steel cubic vacuum vessel, surrounded on all sides with 44 g cm −2 of polypropylene pellets to shield against neutrons from the cavern walls. The vessel was filled with a mixture of 30:10:1 Torr CS 2 :CF 4 :O 2 gas, and sealed for the duration of each run. This departure from the normal mode of operation, in which gas is flowed at a constant rate of one complete vacuum vessel change (590 g) /d, was necessary due to safety concerns over sources of ignition in the constant flow system. These concerns have since been addressed with modifications to the gas system.The DRIFT-IId NITPC consists of a thin-film (0.9 µm aluminised Mylar), texturised central cathode [25] at a potential of -31.9 kV faced on either side by two 1 m 2 multi-wire proportional chambers (hereafter, the 'left' and 'right' MWPCs) at a distance of 50 cm. In this way, two 50-cm-long drift regions are defined. A field cage of 31 stainless steel rings on either side steps down the voltage smoothly between the central cathode and the MWPCs to ensure a uniform electric field of 580 V cm −1 throughout the drift regions. The MWPCs are made up of a central grounded anode plane of 20 µm diameter stainless steel wires with 2 mm pitch, sandwiched between two perpendicular grid planes of 100 µm wires at -2884 V, again with 2 mm pitch and separated by 1 cm from the anode plane. A full description of the detector can be found in Ref. [30].Both the inner grid and anode planes have every eighth wire joined together and read out as one, such that a single 'octave' of wires reads out 8 × 2 = 16 mm in x and y: large enough to contain the recoil events of interest. The outermost 52 (41) wires of the 512 total on the inner grid (anode) planes are grouped together into x (y) veto regions, reducing the fiducial volume of the detector to 0.80 m 3 . The anode and grid veto signal...
Weakly interacting massive particles ͑WIMPs͒ are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion time projection chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with very high sensitivity and background rejection and a robust statistical signature for WIMP interactions.
The combination of the track etching method and atomic force microscopy allows us to search for weakly interacting massive particles (WIMPs) in our Galaxy. A survey of 80720 p, m of 0.5 Gyr old muscovite mica found no evidence of WIMP-recoil tracks. This enables us to set limits on WIMPs which are about an order of magnitude weaker than the best spin-dependent WIMP limits. Unlike other detectors, however, the mica method is, at present, not background limited. We argue that a background may not appear until we have pushed our current limits down by several orders of magnitude.PACS nombers: 95.35.+d, 14.80.Ly, 29.40.Ym, 61.72.Ff Much research is being devoted to the questions of the nature and detectability of the dark matter that comprises more than 90% of the mass of the Universe [1]. One of the most promising candidates is a weakly interacting massive particle (WIMP) which is being sought with instruments capable of detecting the -keV/amu recoiling ions which would be produced in elastic collisions between WIMPs and nuclei [1]. The best limits on the mass and scattering cross section of WIMPs trapped in the Galactic halo result from the use of natural Ge, NaI, and CaF detectors [2]. These limits, however, fall short, by several orders of magnitude, of ruling out one of the favored WIMP candidates, the neutralino [3]. We show here that the natural mica crystals, with an integration time of -10 yr, can record and store the tracks of recoil nuclei struck by WIMPs, and that these tracks can be measured with an atomic force microscope (AFM). Our approach is an extension of the etching method for studying ancient tracks in minerals [4,5]. With it, we report a new limit that is about an order of magnitude weaker than the best spin-dependent limits from NaI and CaF detectors, but show that we have the potential to push these limits down by several orders of magnitude.As with the Ge, NaI, and CaF detectors, mica serves both as the target and as the detector. Muscovite mica is primarily composed of 'H (I = 2), '60 (I = 0), 27A1 (I = 2), Si (I = 0), and K (I = 2). The range of one of these nuclei with a typical recoil energy of -keV/amu is only a few hundred angstroms [6] and the etched depth is even smaller.Although such etched tracks cannot be studied with an optical microscope, we have shown that their dimensions can be accurately measured with an AFM [7]. As shown in Fig. 1, the technique is to cleave open a mica crystal, etch the freshly exposed surfaces, and use an AFM to scan and measure the tracks crossing the cleavage plane. For each area scanned (typically 40 p.m X 40 p, m) a 256 x 256 grid of heights is obtained and fitted line by line (to remove the effect of the piezo motion on the heights) with a fourth order polynomial using a robust fitting algorithm [8]. New, fiattened heights are calculated from the difference between the old height (a) WIMP (b) FIG. 1. An illustration of the etching technique. (a) If WIMPs exist they would cause the constituent atoms of muscovite mica, mainly ' 0, Al, Si, and K, to r...
MeV-GeV dark matter (DM) is theoretically well motivated but remarkably unexplored. This proposal presents the MeV-GeV DM discovery potential for a ∼1 m 3 segmented CsI(Tl) scintillator detector placed downstream of the Hall A beam-dump at Jefferson Lab, receiving up to 10 22 electrons-on-target (EOT) in 285 days. This experiment (Beam-Dump eXperiment or BDX) would be sensitive to elastic DM-electron and to inelastic DM scattering at the level of 10 counts per year, reaching the limit of the neutrino irreducible background. The distinct signature of a DM interaction will be an electromagnetic shower of few hundreds of MeV, together with a reduced activity in the surrounding active veto counters. A detailed description of the DM particle χ production in the dump and subsequent interaction in the detector has been performed by means of Monte Carlo simulations. Different approaches have been used to evaluate the expected backgrounds: the cosmogenic background has been extrapolated from the results obtained with a prototype detector running at INFN-LNS (Italy), while the beam-related background has been evaluated by GEANT4 Monte Carlo simulations. The proposed experiment will be sensitive to large regions of DM parameter space, exceeding the discovery potential of existing and planned experiments in the MeV-GeV DM mass range by up to two orders of magnitude. 4We propose a beam-dump experiment to search for light (MeV-GeV) Dark Matter (DM). DM in this mass range is motivated by both experimental and theoretical considerations. On the theory side, simple extensions to the Standard Model (SM) can accommodate DM-SM interactions that yield the observed DM cosmological abundance. On the experimental side, such models also generically feature particles that explain the currently discrepant value of the muon's anomalous magnetic moment and resolve anomalies in astrophysical observations, while simultaneously evading cosmological and direct-production constraints.This experiment could be performed by placing a detector downstream of one of the JLab experimental Halls to detect DM particles that could be produced by the electron beam in the dump, pass through surrounding shielding material, and deposit visible energy inside the detector by scattering off various target particles or -if unstable -by decaying inside the detector volume. A new underground facility placed ∼ 20m downstream of the beam dump of the experimental Hall-A will host the detector, serving as a general-purpose facility for any future beam-dump experiments. The run would be completely parasitic without affecting the normal operations and the physics program of the Hall. The most striking signal that this experiment would look for consists of events with ∼ GeV electromagnetic energy deposition. With the detector and the experimental set-up we are proposing, this signal will be easily detected over a negligible background. This striking signature can arise in two classes of models: in those where DM scatters elastically off atomic electrons in the detector, an...
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